Measurements of the angle-rate-of-change with a long baseline interferometer (LBI) allows for a method of passively determining the range to an RF emitter. In general, this leads to rapid and more accurate results than conventional triangulations performed via angle-of-arrival (AOA) measurements. This improvement stems from the well-known relationship between the angle-rate-of-change (AROC) and the phase-rate-of-change (PROC), with accuracy enhancements due to the large ratio between the LBI-arm length (dLBI) and radiation wavelength (λ). The relationship leads to an algorithm which substitutes the sequential angle measurements in conventional triangulation schemes with precision phase-rate-of-change (PROC) determinations.
Prior PROC geo-location implementations, however, had problems meeting desired geo-location accuracies because, as LBI baselines and PROC time intervals are increased, the number of range ambiguities increases to the point where geo-location algorithms cannot dependably determine a unique location estimate for the RF emitter.